Non-thermal, non-equilibrium DBD plasma plumes/jets are known in the prior art and have many medical and engineering applications including wound healing, wound sterilization, blood coagulation, scar treatment, surface decontamination, surface treatment, and plasma sterilization. The plume of non-equilibrium DBD plasma generators is discharged in open air and does not require any special plasma enclosure. Therefore, the plume can be located at any distance from the application target without interference with the generator structure. Furthermore, the risk of contamination from contact with or adherence between the application target and plasma enclosure is eliminated.
The precise chemical/biological reaction mechanism between the plasma plume and the target, which produces the aforementioned beneficial effects, is still under investigation. Several theories have been proposed.
According to one theory, the presence of various gases along with moisture in the air produce several chemically reactive species in the plasma plume that react with the target. Chen's work shows that the plasma effluent of the plume carries an abundance of reactive atomic oxygen (RAO), which is the catalyst for plasma medical effects. As RAO reacts with H2O in blood, it produces H2O2. Some of the H2O2 is decomposed to oxygen, which dissolves into tissue to increase oxygen tension. H2O2 also triggers fibroblast growth factor, platelet derived growth factor and other factors to induce reactions such as inflammation and angiogeneis. As a result, the healing process is improved and healing time is reduced. Chen C., Air Plasma Effects on Bleeding Control and Wound Healing, PhD Thesis, Department of Electrical Engineering, Polytechnic Institute of NYU, June 2011, UMI Number: 3457994.
According to another theory, radicals in plasma support the endogenous radical-mediated defenses and healing mechanisms of tissue and derive the formation of cell mediators such as nitric oxide. For example, Laroussi et al. concluded that for non-equilibrium, atmospheric air plasmas, oxygen-based and nitrogen-based reactive species played the most important role in the bacterial inactivation process Lederer E., Plasma Blows Wounds Clean, http://news.doccheck.com/com/article/211278-plasma-blows-wounds-clean/.
According to Soffels et al., plasma releases controllable amounts of short-lived reactive oxygen (ROS) and nitrogen (RNS) species that address only the target areas in the tissue. Each of these species has different physiological functions such as antibacterial, pro-apoptotic, pro-inflammatory (ROS), or anti-inflammatory and pro-apoptotic (RNS). External administration of ROS or RNS by plasma locally reinforces the natural physiological processes. Stoffels E., Roke A. J. M., Deelman L. E., Delayed Effects of Cold Atmospheric Plasma on Vascular Cells, Plasma Processes and Polymers, No. 5, 2008, 599-605.
Regardless of the mechanism, it has been experimentally confirmed that plasma treatment conditions can be tuned to achieve many desired medical effects, especially in medical sterilization and treatment of different types of skin diseases. Plasma treatment conditions may be tuned by, for example, varying the treatment conditions and/or plasma characteristics including the degree of ionization, electron's temperature, gas temperature, input power (voltage) of the generator, input gas composition, exposure time to the plasma plume, and distance between the plasma plume and the target.
In general, prior art plasma generators use two electrodes, such as parallel, metallic plates, separated by a dielectric material. Typically, the electrodes are fixed relative to one another, which stagnant configuration produces the same plume characteristics for a give set of input values. It would be desirable to provide a plasma generator having one or more electrodes that are movable, which relative movement provides another means of changing or tuning the characteristics of the plasma plume.
Many prior art plasma generators also require high input power, complex heavy-duty pulse generators, amplifiers, or complicated RF generators in order to create the plasma-generating electric field. Such electrical requirements greatly inhibit the portability of such devices and significantly add to the cost of production. Therefore, it would be desirable to provide a plasma generator that has basic components and low power requirements so that the device can operate portably with a low voltage battery source.